Lattice disorder in implanted insulators: Pb implantation in α-Al2O3

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Abstract
The effects of 20, 50 and 100 keV Pb ion implantation on α-A12O3 single crystals have been investigated using the Rutherford backscattering channeling technique. Lattice disorder is observed to reach saturation at Pb doses greater than 1015 ions/cm2. Analysis of the implantation and damage profiles reveals that migration of defects occurs during implantation. It is found that the average threshold displacement energy, obtained from the measured number of displaced lattice atoms using the Kinchin-Pease equation, is dependent on implantation energy. This is discussed in terms of lattice reordering during ion bombardment which depends on the substrate temperature. The lowest value of the average displacement energy, obtained from the 20 keV samples, is 14 ± 2 eV, in reasonable agreement with the calculated Frenkel pair formation energy in α-A12O3. Lattice locations for {0110} and {1212} configurations show that the implanted Pb atoms are almost substitutional along the A1 rows. The substitutional fraction reaches a value of about 80% at an implantation dose of 1014 ions/cm2. Post-implantation annealing experiments indicated a degree of correlation between Pb migration and lattice damage recovery.